refactor: Create method for skipping ParseObject keys

[cbaker6]

New Pull Request Checklist

• I am not disclosing a vulnerability.
• I am creating this PR in reference to an issue.

Issue Description

Approach

TODOs before merging

• Add tests
• Add entry to changelog
• Add changes to documentation (guides, repository pages, in-code descriptions)

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (e54ac22) 91.36% compared to head (098d3e1) 91.68%.

Files	Patch %	Lines
Sources/ParseSwift/Coding/ParseEncoder.swift	95.65%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #144      +/-   ##
==========================================
+ Coverage   91.36%   91.68%   +0.31%     
==========================================
  Files         178      178              
  Lines       15504    15511       +7     
==========================================
+ Hits        14165    14221      +56     
+ Misses       1339     1290      -49     

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